felezjoo PI(the best pulse induction metal detector that I made until now)

[jladre]

I use multilayer for all 100n caps, is that bad?

It will work fir sure but ceramic capacitors are somewhat non-linear in their frequency and voltage responses, compared to film capacitors. Another issue with ceramic capacitors is that they tend to behave as microphones, thus picking up ambient sound and modulating the voltage across them accordingly.

[jladre]

You need to change the value of R20 to conpensate to the battery monitor.

[ripsdevala]

I use multilayer for all 100n caps, is that bad?

[ripsdevala]

Hi,
Your 7812 drains too much current.
It's made for 1A.
If the resistance between +12 and GND is less than 12ohms, the 7812 will not work for long.
Check for shortcut on the +12v line.

No short at all, or my bc337 cause it, i reverse the orientation following the the legs CBE, mine have EBC.

Its better to remove your ste up converter and used only the 3x3.7 lit-ion battery then remove the 7812 regulator.. mine works perfect without it.

Remove and make new connection to 12v track right?

Done... Work okay, but noisy, maybe im bellow florecent lamp

[jladre]

Beware also those fairchild regulator and mosfet they will become very hot compare to expensive one.

[jladre]

Anyone know why my Mc7812CT+heatsink is hot? Cant touch it more than 2 sec.
Using 3xLi-ion+step up to 18v

Its better to remove your ste up converter and used only the 3x3.7 lit-ion battery then remove the 7812 regulator.. mine works perfect without it.

[reptooyep]

Hi,
Your 7812 drains too much current.
It's made for 1A.
If the resistance between +12 and GND is less than 12ohms, the 7812 will not work for long.
Check for shortcut on the +12v line.

[ripsdevala]

Anyone know why my Mc7812CT+heatsink is hot? Cant touch it more than 2 sec.
Using 3xLi-ion+step up to 18v

[Geo]

If the op.amp has lower noise then it is possible to get more depth. Also if it has better bandwidth we can give to it more gain.
LF357 has typican noise 12nv/sqr hz and the same has the OPA627. Opa637 is better.
LME49999 (if it works) has 0.9nv and bandwidth 110Mhz. So with this hight bandwith to be possible to give gain = 3000 or more and to see a better depth.
But i am not sure because Mr Hamid maybe to made all those tests.
From the other side it is Winter and i have not something better to do.

[eclipse]

Different op amps won't give you performance boost as you might expect. You can try 20$ op amps (I did - with OPA627) and you won't get any boost in performance.
My suggestion is to try different coils.. or if you're up to the task construct +5V boost voltage for op amp & 2 stage op amp structure, but it will require quite a bit of tweaking.
Pretty much dead project for improvements as far as I'm concerned... unless the developer doesn't release in public the code, which won't happen anytime soon.

[jladre]

HiJladre.
I am sure that Mr Hamid tried to make a very good detector with very cheap components. So i play with better (and more expensive) components that i have at my Lab drawer to see if any other op.am gives better results. I am sure that mr Hamid knew what he wanted to do and what he did and i thank him for this project.

[Geo]

Before mr.Hamid come up to design this machine he already tested all or almost those amplifier and found out and believe that lf 357n and lf357h are the only available that can give optimal results.. this people mr. Hamid and koohyar are nice to talk but they are been offended when criticise and look-down..

HiJladre.
I am sure that Mr Hamid tried to make a very good detector with very cheap components. So i play with better (and more expensive) components that i have at my Lab drawer to see if any other op.am gives better results. I am sure that mr Hamid knew what he wanted to do and what he did and i thank him for this project.

[Geo]

Hi Green.
I believe that there is problem with ICs Fault) because they consumption 50ma, it is a very hight current for an op.am.
Any way there is not problem to check it again and play with R13 ( i have a trimmer at place of R13 so no problem).

[green]

Also i tried 2 ICs LTE49990 at place of LF357 but did n't work at all. Any idea why??????

Hi Geo
Another try at why a LME49990 doesn't work. Spec sheet has the + common mode voltage at +supply minus 3 or 4volts. The LF357 specs. to just above the +supply. R13 and R14 set the voltage at 9.5volts(2.5 volts below +supply). You could shunt R13(18k) with 18k to 22k to see if the LME49990 output works.

[jladre]

Before mr.Hamid come up to design this machine he already tested all or almost those amplifier and found out and believe that lf 357n and lf357h are the only available that can give optimal results.. this people mr. Hamid and koohyar are nice to talk but they are been offended when criticise and look-down..